{
 Gann Box Drawing Tool
 written by Lawrence Chan
 copyright (c) 2005 by TickQuest Inc.
 Jun 20, 2005
}

function toolname : string;
begin
   result := 'GannBox';
end;

function numpoints : integer;
begin
   result := 2;
end;

procedure add_next_line (c, x1, y1, x2, y2 : integer; var list : variant; var i : integer);
begin
   list [i] := c;

   list [i + 1] := x1;
   list [i + 2] := y1;
   list [i + 3] := x2;
   list [i + 4] := y2;

   i := i + 5;
end;

procedure draw2 (
            boundary, xlist, ylist, prices, hlist, vlist, flist, clist;
            var command_list : variant);
var i, j, x1, x2, x3, x4, y1, y2, y3, y4, lb, ub, hsize : integer;
    delta, udelta, xdelta, arraysize : integer;
    bound_left, bound_top, bound_right, bound_bottom : integer;
    v, udelta2 : double;
    draw_hmult : boolean;
begin

   // 2 control points are enough

   x1 := xlist [0];
   x2 := xlist [1];

   y1 := ylist [0];
   y2 := ylist [1];

   // grab the boundary points

   bound_left := boundary [0];
   bound_top := boundary [1];
   bound_right := boundary [2];
   bound_bottom  := boundary [3];

   // initialize the resulting commands for a single line

   arraysize := 5;
   RedimVarArray (command_list, arraysize);

   //

   i := 0;

   // diagonal lines drawn from top to bottom

   delta := y2 - y1;

   udelta := delta;
   if delta < 0 then
      udelta := - delta;

   if delta = 0 then
      add_next_line (5, x1, y1, x2, y2, command_list, i)
   else
   begin

      y3 := y1 - int ((y1 - bound_top) / udelta) * udelta;

      xdelta := x2 - x1;
      if xdelta < 0 then
         xdelta := - xdelta;

      if xdelta <> 0 then
         y3 := y3 - int ((bound_right - bound_left) / xdelta) * udelta;

      y4 := y3 + udelta;

      x3 := x1;
      x4 := x2;

      while y3 < bound_bottom do
      begin
         add_next_line (5, x3, y3, x4, y4, command_list, i);

         y3 := y3 + udelta;
         y4 := y4 + udelta;

         arraysize := arraysize + 5;
         RedimVarArray (command_list, arraysize);
      end;

   end;

   // diagonal lines drawn from bottom to top

   if delta = 0 then
      add_next_line (5, x1, y2, x2, y1, command_list, i)
   else
   begin

      y3 := y1 - int ((y1 - bound_bottom) / udelta) * udelta;

      if xdelta <> 0 then
         y3 := y3 + int ((bound_right - bound_left) / xdelta) * udelta;

      y4 := y3 - udelta;

      x3 := x1;
      x4 := x2;

      while y3 > bound_top do
      begin
         add_next_line (5, x3, y3, x4, y4, command_list, i);

         y3 := y3 - udelta;
         y4 := y4 - udelta;

         arraysize := arraysize + 5;
         RedimVarArray (command_list, arraysize);
      end;
   end;

   // horizontal lines drawn from top to bottom

   if delta <> 0 then
   begin

      udelta2 := udelta / 2;
      y3 := round (y1 - int ((y1 - bound_top) / udelta2) * udelta2);

      j := 0;
      y4 := y3;

      x3 := x1;
      x4 := x2;

      while y4 < bound_bottom do
      begin
         add_next_line (5, x3, y4, x4, y4, command_list, i);

         inc (j);
         y4 := round (y3 + j * udelta2);

         arraysize := arraysize + 5;
         RedimVarArray (command_list, arraysize);
      end;

   end;

   // first vertical line

   add_next_line (6, x1, y1, x1, y2, command_list, i);


   // clean up

   RedimVarArray (command_list, i);

end;